Unlike equity securities, most fixed income securities (e.g., bonds) are currently bought and sold in the over the counter (OTC) market. The OTC market generally comprises securities firms and banks that trade fixed income securities either by phone or electronically. Some firms and banks act as dealers who keep an inventory, and buy and sell securities for their own account. Others act as brokers and buy from or sell to other dealers in response to specific requests for liquidity on behalf of their customers. As such, the current fixed income security model consists of manual, person-to-person exchanges in two different markets. The first market is the dealer to dealer market. The second market is the dealer to customer market. The first market generally trades with higher transparency than the second market, and with tighter bid offer spreads. The second market generally trades with lower transparency and wider bid-offer spreads.